Thickened cleaning compositions are well known in the art, and have found various applications for instance in the context of hard surface or laundry cleaning compositions.
The simplest way to make such compositions is to add a thickener on top of a non-viscous product. However, thickeners can be seen as undesirable in many respects, such as processing issues, long term product stability issues as well as other considerations related to formula cost. It is thus desirable to formulate a cleaning composition which is viscous, but does not necessarily contain a thickener.
The art teaches that it is possible to do so by using a system where viscosity is built by combining an anionic surfactant together with an electrolyte in an aqueous medium, wherein the viscosity can be adjusted by balancing both ingredients. This system is very often used in the formulation of shampoos, but has also found application in cleaning compositions. In theory, this solution can be used with any anionic surfactant, but the compositions of the present invention only use an alkyl sulfate anionic surfactant derived from natural coconut oil; indeed, this surfactant provides good performance and is particularly desirable for obvious environmental reasons.
Thus, self-thickened compositions can be made which comprise such an anionic surfactant derived from natural coconut oil and an electrolyte. The viscosity of such a composition is of course sensitive to temperature, and a new technical problem has been identified in that such compositions are not physically stable at low temperature, where the product undergoes phase separation; As a result, the product has an aesthetically unacceptable aspect.
It has now been found that this problem could be solved by using a specific electrolyte and adding to the system above a nonionic surfactant from a selected class.
Canadian patent CA 1 194 381 discloses scouring compositions containing anionic surfactants, an electrolyte and an ethoxylated alcohol surfactant.
European patent EP 116 905 teaches the use of an ethoxylated and/or propoxylated alcohol surfactant to reduce the viscosity of industrial-grade synthetic anionic surfactant concentrates.
European patent application EP 329 209 discloses scouring compositions comprising a surfactant, an electrolyte and a solvent to build viscosity.